Unable to load Linux after re-installing windows

Mohit_taneja · 06-18-2008, 02:55 AM

Hi everyone,

I had a dual boot on my system with Windows XP(sp-2) and ubuntu 7.04. But due to some reasons windows crashed and I had to re-install windows.Now when i start, my computer instead of loading Grub loads windows without detecting the already present linux installation. Now do i need to re-install Grub (If yes, then how) or something else. I also read about using something like a rescue disk, but the live cd that I have for ubuntu 7.04 does not have any such feature.

So, it would be great if someone could help me out with this.
I just hope that I don't have to re-install ubuntu.

Thanks in advance,
Mohit

jomen · 06-18-2008, 03:20 AM

Quote:

the live cd that I have for ubuntu 7.04 does not have any such feature.

but you can use it to boot the machine...

Then mount the linux partition if this is not done automatically.
Check if the contents in /boot/grub/menu.lst are still correct (if you just reinstalled windows they will be and you can as well skip this step).
issue:
grub-install --no-floppy /dev/hdx (hdx being the drive you boot from)
and you are good.
This will reinstall grub as it where - windows always overwrites the bootloader with its own when you install it and I know of no way to prevent it from doing that - so reinstalling grub after a windows install is "standard procedure".
[edit]
I think that works - but it might not...I did not test.

But this will: (change "yourharddisk")

Code:

mkdir /mnt/ubuntu
mount /dev/yourharddisk /mnt/ubuntu
mount -t proc none /mnt/ubuntu
mount -o bind /dev /mnt/ubuntu
chroot /mnt/ubuntu /bin/bash --login
source /etc/profile
grep -v rootfs /proc/mounts > /etc/mtab
grub-install --no-floppy /dev/yourharddisk

mamboze · 06-18-2008, 03:41 AM

I had exactly the same problem about 6 months ago with dual boot Feisty Ubuntu and WinXP. Reinstalling Windows wipes out info on the MBR (or so I understand, I'm a newbie in this stuff too).

At any rate, the solution is pretty straightforward. First of all, get a Super Grub Recovery disk. You can download an iso file here:

http://forjamari.linex.org/frs/?grou...ase_id=620#620

and there's some stuff on Super Grub here:

http://www.linux.com/articles/57240 and elsewhere

Boot from the disk and then follow the menu to get to the MBR repair menu. As I said I went thru all this stuff about six months ago and I don't remember all the details. But the Super Grub menu system has a good help section and is not that hard to follow.

Anyhow, after fixing the MBR, Ubuntu booted perfectly, exactly as before, as you would expect

.

Hope this helps

Roy

jomen · 06-18-2008, 03:58 AM

This recovery disk will probably work - but one has to download and burn it.
Mohit_taneja already has a suitable disk - the Ubuntu live-cd.
With the approach I described the version of grub present on the Ubuntu installation will be used - the potential for version mismatches between grub and its files in /boot/grub is eliminated.
With "chroot" you are using the system itself to do the job.
I have done this lots of times and it seemed the natural and easy solution...the gentoo way

Mohit_taneja · 06-18-2008, 11:40 PM

Well, I have fixed the problem.I found that one
needs to re-install Grub in such a case as windows overwrites the MBR
(master boot record).
I booted from the live cd from which i could run grub from terminal " sudo grub"
In grub one can find the location for the root and re assign it and
overwrite the MBR.
"grub> find /boot/grub/stage1"
to find the root this will print the hard disk number and the
partition number for root, you can reassign the root as follows
"grub> root (hd0,2)"
in case the previous command gave this out put which means that the
root or linux is present at the first hard disk and third partition
and then
"grub> setup (hd0)"
to install grub in that hard disk
and then quit
"grub> quit"
now on rebooting the system, my system loaded grub to choose which os
do i need to boot from instead of directly booting Windows.

Thanks,
Mohit Taneja